Storage-stable precursors for rigid polyurethane foams

Abstract

Diorganotin compounds wherein at least one of the remaining valences on the tin atom is satisfied by a sulfur atom or a thiocyanate group are unique among diorganotin compounds in that they retain their catalytic activity over extended periods of time in the presence of the precursors or masterbatches conventionally employed to prepare rigid, cellular polyurethanes.

What is claimed is: 
     
       1. In an improved method for preserving catalytic activity during long term storage of precursors for rigid cellular polyurethanes wherein said precursor comprises a polyol containing at least two active hydrogen atoms, as determined by the Zerewitinoff method, and a catalytically effective amount of an organotin compound as the gel catalyst, the improvement which consists of storing said polyol in the presence of a gel catalyst selected from the group consisting of R 2  Sn(SCN) 2 , [R 2  Sn(SCN)] 2  O, (R 2  SnSCN) 2  S, (R 2  SnX) 2  S and R 2  SnS, wherein R is a monovalent hydrocarbon and X is chlorine, bromine or iodine. 
     
     
       2. A method according to claim 1 wherein the gel catalyst is a diorganotin sulfide or a diorganotin dithiocyanate. 
     
     
       3. A method according to claim 1 wherein R is selected from the group consisting of alkyl containing from 1 to 12 carbon atoms, cycloalkyl, phenyl, aralkyl and alkaryl, wherein the alkyl portion of said aralkyl and alkaryl groups contain from 1 to 12 carbon atoms. 
     
     
       4. A method according to claim 3 wherein R is phenyl. 
     
     
       5. A method according to claim 3 wherein R is methyl, butyl or octyl. 
     
     
       6. A method according to claim 5 wherein R is butyl. 
     
     
       7. A method according to claim 1 wherein the polyol is combined with at least one member of the group consisting of (a) a silicon-containing surfactant in an amount from about 1 to 5 parts by weight per 100 parts of said polyol, and   (b) a blowing agent in an amount from about 10 to 50 parts by weight per 100 parts of said polyol, and   (c) a catalytically effective amount of a tertiary amine.   
     
     
       8. A method according to claim 7 wherein said tertiary amine is selected from the group consisting of dimethylcyclohexyl amine, N-ethyl morpholine and triethylene diamine. 
     
     
       9. A method according to claim 7 wherein said blowing agent is a chlorine-containing hydrocarbon and boils from 35 to about 80° C. 
     
     
       10. A method according to claim 1 wherein said polyol is a polymer of propylene oxide. 
     
     
       11. A method according to claim 1 wherein said gel catalyst is present at a concentration of from 0.1 to 10 parts by weight per 100 parts of polyol.